Method of and apparatus for the casting of metal



Dec. 10, 1957 W. C. F. HESSENBERG ETAL METHOD OF AND APPARATUS FOR THECA STING OF METAL Filed June 21, 1955 FIG.1

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28 22 fii I EV Q 31 5 1 27; g 2 H l'w 2 F 10 INVENTORS WILFRID CF.HESSENBERG JOHN SAVAGE ATTORN EY Unied States METHOD OF AND APPARATUSFOR THE CASTING OF METAL Application June 21, 1955, Serial No. 516,996

Claims. (Cl. 22-57.2)

This invention relates to the casting of metals, and more particularlyto a method of and apparatus for the continuous casting of high meltingtemperature metals such as ferrous alloys.

In the continuous casting of metals various systems of casting are used,although all continuous casting involves the delivery of a stream ofmolten metal to an open ended fluid cooled casting mold in which anembryo casting is formed and from which the casting is withdrawn by awithdrawal mechanism. Many of the continuous casting systems areoperated in such a manner as to cause a relative movement between themold and the casting during one portion of the casting operation whileduring another portion of the casting operation the casting ismaintained stationary relative to the wall of the mold. In onecontinuous casting system the mold is oscillated in a direction axiallyof the casting in a predetermined timed pattern, while the casting iswithdrawn by the withdrawal mechanism at a substantially uniform rate.In another system of continuous casting the casting is continuouslywithdrawn and the mold is arranged for axial movement thereof inaccordance with the friction between the casting and the wall of themold. When the frictional forces between the casting and the mold aresufiicient the mold is moved axially with the casting so that norelative movement therebetween occurs. As the mold moves, the forcespreventing move ment of the mold gradually increase until this forceovercomes the frictional force between the casting and the mold, and themold is returned to its previous position. In yet another system ofcontinuous casting, the mold is stationary and the withdrawal mechanismis operated in a predetermined timed pattern so that the castingwithdrawal is stopped periodically, and then moved so that alternatelyno relative movement occurs between the casting and the mold.

During the continuous casting of metal there is a atent tendency for theinitially solidified metal forming the from the mold and necessitates astoppage of the casting process.

Each of the above described systems of continuous casting operation haslargely overcome the sticking tendency of the casting to the mold wall,or has at least alleviated the rupture tendency of the casting undersuch conditions. skin on the casting has not altogether been avoided inany of the known continuous casting systems. In this connection it willbe understood that if a perfect method of lubricating the mold wall waspossible, the casting skin would not stick to the mold wall. However, inactu- However, the rupture of the initially formed al practiceperfection of lubrication has not been at tained since at leastoccassionally there will be a tendency for the casting skin to stick tothe mold wall and to rupture the casting.

In accordance with the present invention the rupture of the initiallyformed casting skin, by reason of its adhesion to the mold wall, hasbeen largely overcome. This is accomplished according to the invention,by applying a compressive force to the billet so as to release thecasting before relative movement occurs between the casting and the moldwall so as to prevent the sticking of the skin to the wall of the mold.The compressive force is applied to the casting in a direction oppositeto the normal direction of the casting withdrawal from the mold.

The compressive release force may be applied to the casting by theapplication of a force in a direction opposite to that of the castingwithdrawal, or the compressive release force may be applied to the mold.The application of the compressive release force may be governed by thefriction of the casting on the mold wall during relative movementtherebetween, which is an indication of adhesion between the casting andthe mold.

The various features of novelty which characterize our invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which we have illustrated and described preferred embodimentsof the invention.

Of the drawings:

Fig. 1 is an elevation, in section, of a continuous casting mold whichis spring mounted and constructed in accordance with the presentinvention.

Fig. 2 is an elevation, in section, of a modified application of theinvention to a continuous casting mold; and

Fig. 3 is a still further modification of the invention as applied to astationary continuous casting mold.

The present invention may be applied to any of the continuous castingsystems wherein alternative relative movement and no relative movementoccurs between the continuous casting mold and the casting therein. Inany of the casting systems described, the compressive release concept ofthe invention is applied to cause a compression of the casting so as tobreak the adhesion of the casting relative to the mold immediately priorto the occurrence of relative movement between the casting and the mold.The compressive release concept can be applied in a uniform timed cycleto either the mold or the casting or the compressive release impulse canbe imposed as required when the friction between mold and castingexceeds a selected value.

Referring first to Fig. l, the continuous casting mold 10 is providedwith a cooling jacket 11 through which a cooling liquid, such as water,passes. The cooling liquid enters by an inlet pipe 12 and leaves themold jacket by an outlet pipe 13. The mold 10 is mounted on a top plate14 extending beyond the periphery of the cooling jacket 11 and issupported for vertical movement by three compression springs 15circumferentially equally spaced around the mold. The springs 15 aremounted on the surface 16 of an annular recess 17 of a support member18. Aligned with the springs 15 and mounted be tween the top of therecess 17 and the upper surface of the plate 14 are three pneumatic rams20. These rams are of a type which provide a sudden impact on the plate16 upon the application of compressed air to the inlet pipes 21. Therams may be, for example, of a type frequently employed as pneumatichammers.v Astream of molten steel, as indicated at 22, is poured intothe top of plate.

the mold from suitable molten metal delivery means (not shown). Thesteel solidifies within the mold and the casting 23 is continuouslywithdrawn from the bottom of the mold by a withdrawal mechanism, such asthe pinch rolls indicated at 24.

Providing that there is no sticking of the casting within the mold 10,the mold will remain in a substantially stationary position, with thecasting 23 being continuously withdrawn from the lower end of the mold.When sticking between the casting and the mold occurs, the increase inthe frictional force therebetween applies a downwardly moving force tothe mold 10 which acts against the springs 15. When the friction betweenthe casting and the mold reaches a predetermined value, compression ofthe springs by reason of the downward movement of the mold plate 14engages a contact 25 at a preselected distance below the normal positionof the plate 14. The contact 25 controls a solenoid operated pilot valve(not shown) for the delivery of compressed air to the rams 20. Thedelivery of compressed air to the rams cause an impulse force to bedelivered to the mold, which causes the mold to move downwardly at aspeed greater than the withdrawal speed of the casting. This downwardforce on the mold releases the casting from the mold wall, and causescompressive forces to be applied to the casting to release the castingfrom adhesion to the mold so that the casting can be withdrawn withoutrupture of the skin of the casting.

The location of the contact 25, the strength of the springs 15, andother design factors of the mold arrangement are determined by the sizeof the casting and the rate of casting withdrawal from the mold. By wayof example, a 4" square casting withdrawn at a rate of 24" per minute,produced in an apparatus of the type disclosed in Fi l, utilized springs15 having a compressive strength of 45 pounds per inch of springcompression. Under these conditions the control contact 25 was locatedso as to be actuated after a l downward movement of the mold 10. Whensupplied with compressed air of 80 pounds per square inch pressure, eachof the rams released a downward thrust on the mold 10 equal toapproximately 192 pounds which resulted in a downward movement of themold of approximately /2. After the rams 20 had been actuated the moldreturned to its original position, as guided and dampened by the springs15 which in this instance served as shock absorbers.

In the embodiment of the invention shown in Fig. 1, one purpose of thecompressive springs 15 is to regulate the application of the compressiverelease force by the rams. It will be further understood that othermeans can be used to actuate the application of forces on the mold forthe compressive release of the casting from the mold.

In the modification of the invention shown in Fig. 2, the mold 10 issubstantially the same as that shown in Fig. 1 and the casting 23 iscontinuously withdrawn by the pinch rolls 24 as described in connectionwith Fig. 1. In the Fig. 2 version of the invention the mold 10 ismounted on a support 26 by three compression springs 27 acting againstthe top plate 28. In this modification of the invention, the compressiveforce on the billet is cyclically applied and is not limited tooperation only when sticking or adhesion occurs between the casting andthe mold wall. In this arrangement, adhesion between the casting and themold wall is prevented, rather than released after it has occurred as inthe arrangement of Fig. 1. As shown, the top plate 28 is provided with apair of cams 30 having their surfaces bearing on the The cams arecontinually driven from the driving means of thepinch rolls 24 so thatthe cams 30 operate in concert with the pinch rolls. The profile of thecam .surfaces is such that during their operation the mold is caused tomove downwardly at a speed greater than the I cycle the mold 10 isreturned quickly to its initial position under the forces exerted by thecompressed springs 27. Thus, over the majority of the time in which thecasting is being withdrawn the mold 10 is moving downwardly at a higherrate than the casting, so as to apply a compressive force to thecasting, and thus prevent adhesion between the casting and the mold.

The rate and amplitude of the movement of the mold 10 is dependent uponthe size of the casting produced and the rate of casting withdrawal.With a 4" square casting, withdrawn at a speed of 24" per minute, therate of downward movement of the mold should be at least 1% times thespeed of the casting withdrawal during the major portion of the cammingcycle. During upward movement of the mold 10, the mold speed should beapproximately five times the speed of the withdrawal of the casting. Theamplitude of movement of the mold should be at least 1", but with highercasting production rates, the amplitude of mold movement should also beincreased.

In the form of the invention shown in Fig. 3, the casting mold 10 isstationary and supported in a fixed position by structural membersindicated at 31. The mold construction is similar to the constructionillustrated in Figs. 1 and 2 and includes a water cooling jacketprovided with inlet and outlet pipes for the flow of cooling fluidthrough the mold. As shown in Fig. 3, the pinch roll withdrawalmechanism 32 is driven at a suitable speed by, for example, a variablespeed, reversing motor 33.

In this arrangement, the pinch roll withdrawal mechanism 32 is operatedin a cycle of changing speeds, including a period when the casting isstationary in the mold. Thus, the cycle of pinch roll operationsincludes a withdrawal of the casting for a predetermined period of time,and a stoppage of the withdrawal mechanism. Immediately before the pinchroll operating mechanism 32 is restarted for the downward withdrawal ofthe casting, the pinch roll mechanism 32 is operated in a reversedirection to cause the casting to move upwardly within the mold 10. Thisimpulse of upward casting movement is immediately followed by thedownward withdrawal of the casting. The compressive forces of the upwardmovement of the casting releases the casting from the mold wall andsubstantially eliminates rupture of the casting skin during thesubsequent withdrawal operation.

To attain the cycle of pinch roll operations described the motor iscontrolled by a timing mechanism schematically illustrated by thecontrol box 34. The timing mechanism may be of the general typedisclosed in United States Patent 2,682,691 with the addition of acontrol circuit suitable for the reversal of the motor 33 to attain theupward movement of the casting prior to the beginning of the downwardremoval of the casting from the mold.

While in accordance with the provisions of thestatutes we haveillustrated and described herein a preferred embodiment of theinvention, those skilled in the art will understand that changes may bemade in the method of operation and form of the apparatus disclosedwithout departing from the spirit of the invention covered by ourclaims, and that certain features of the invention may sometimes beusedto advantage without a corresponding use of other features.

What is claimed is:

l. The method of continuously casting metal in an open ended fluidcooled mold which comprises the steps of delivering molten metal to saidmold, withdrawing an at least partially solidified casting from saidmold with relative movement therebetween in a first direction,maintaining the casting stationary with respect to the mold during aportion of the casting period, and causing relative movement betweensaid casting and mold in a direction-opposite to said-first direction tocompress the casting within saidrnold before relative movement in saidfirst directionoccurs between said casting and said mold.

'2. The method of continuously casting metal according to claim 1,wherein said casting withdrawal is continuous. I

3. The method of continuously casting metal according to claim 2,wherein said fluid cooled mold is moved in a periodic pattern axially ofsaid casting.

4. The method of continuously casting metal in an open ended fluidcooled mold which comprises the steps of delivering molten metal to saidmold, at least partially solidifying the molten metal within said moldto forma self sustaining casting, continuously withdrawing said embryocasting from said mold, moving said mold axially of and with saidcasting a predetermined distance without relative movement therebetweenin accordance with an increase in friction between mold and casting,imparting an impulse movement to said mold in the direction and at aspeed in excess of said casting withdrawal, and restoring said mold to aselected position by movement axially of said casting and in a directionopposite to said casting withdrawal.

5. The method of continuously casting metal in an open ended fluidcooled mold which comprises the steps of delivering molten metal to saidmold, at least partially solidifying the molten metal within said moldto form a self sustaining casting, continuously withdrawing said embryocasting from said mold, moving said mold axially of said casting with norelative movement between said mold and casting, moving said moldaxially of said casting in the direction of and in excess of saidcasting withdrawal to compress the wall of said casting, and moving saidmold axially of said casting in a direction opposite to said castingmovement immediately after compressing said casting.

6. The method of continuously casting metal according to claim 1,wherein said casting is withdrawn from said mold intermittently, and thecasting is driven into said mold prior to the resumption of castingwtihdrawal.

7. Apparatus for the continuous casting of metal comprising an openended fiuid cooled mold, means for delivering molten metal to one end ofsaid mold, a withdrawal mechanism for withdrawing a casting in a firstdirection from the opposite end of said mold, means for retaining thecasting stationary with respect to said mold during a portion of thecasting period, and means for causing relative movement between saidmoldand casting in a direction opposite to said first direction tocompress the casting within said mold before relative movement occursbetween said mold and casting in said first direction.

8. Apparatus for the continuous castingof metal comprising an open endedfluid cooled mold, means for delivering molten metal to one end of saidmold, a withdrawal mechanism for withdrawing a casting from the oppositeend of said mold, means for reciprocating said mold longitudinally ofsaid casting in timed relation therewith so that the casting isstationary with respect to said mold during a portion of the castingperiod and the mold moves in the opposite direction to said withdrawncasting during another portion of said casting period so that there isrelative movement therebetween, and means for compressing the castingwithin said mold by moving said mold in the same direction as and at agreater rate than said casting before relative movement in said oppositedirection occurs between said mold and casting.

9. Apparatus for the continuous casting of metal comprising an openended fluid cooled mold, compression springs supporting said mold, meansfor delivering molten metal to one end of said mold, means forwithdrawing a casting from the opposite end of said mold, a contactactuated by movement of said mold when the casting adheres to and isstationary with respect to said mold, and means for compressing thecasting within said mold before relative movement occurs between saidmold and casting including a pneumatic hammer positioned to transmit animpulse to said mold in the direction of said casting withdrawal whensaid contact is actuated.

10. Apparatus for the continuous casting of metal comprising astationary open ended fluid cooled mold, means for delivering moltenmetal to one end of said mold, means for withdrawing an embryo castingfrom the opposite end of said mold in an intermittent cycle of operationincluding a timed period when the casting remains stationary withrespect to said mold, and means for compressing the casting within saidmold before relative movement occurs between said mold and casting,including a timed control to reverse the withdrawal mechanism and todrive the casting into said mold.

References Cited in the file of this patent UNITED STATES PATENTS1,088,171 Pehrson Feb. 24, 1914 2,284,704 Welblund June 2, 19422,597,046 Sondzimir May 20, 1952 FOREIGN PATENTS 3,221 Great BritainFeb. 8, 1912 718,644 Great Britain Nov. 17, 1954 674,136 Germany Apr. 5,1939 877,940 Germany May 28, 1953 902,433 Germany Jan. 21, 1954

